Safeguards Implications for Deep Borehole Disposal of Spent Fuel

Filling the gaps of uranium oxide hydrates with magnesium(ii) ions: unique layered structures and the role of additional sodium(i) ions

“…The structure contains six unique U centres, U1 in 6-fold coordination with a tetragonal bipyramid and U2-U6 in 7-fold coordination with pentagonal bipyramids. All six uranyl moieties exhibit the normal uranyl form with near-linear UvO bonds ranging from 1.808 (9) U-Mg2n crystallises in the triclinic P1 ˉspace group. The layered structure (Fig.…”

“…7,8 It is well understood that uraninite (UO 2+x ) as a primary uranium mineral or UO 2 as the primary component of SNF will be gradually oxidised from U 4+ to U 6+ if exposed to oxidative conditions. [9][10][11] As the most stable U 6+ form, the uranyl [(UO 2 ) 2+ ] ion with two strongly bonded axial oxygen atoms is ready to coordinate with O/OH ligands in the equatorial positions forming tetragonal, pentagonal and hexagonal bipyramids, which connect each other via both corner-and edgesharing to form various uranyl-containing compounds, normally in the form of layered structures with various interlayer cations adopted from the surroundings. [12][13][14][15] Uranium oxide hydrate (UOH) minerals are a group of secondary uranium minerals formed in the early stage of uraninite weathering.…”

Investigation of uranium oxide hydrates with barium(ii) ions: structural diversity, uranium valences and implications

“…8 However, there are still concerns on the possible interactions of SNF including fission products and radionuclides from the decay process with the surrounding materials in the presence of underground water. 9 While the geological repositories are designed to have a reducing environment where SNF will remain stable, a possible accident could occur where underground water may be in contact with SNF during the long-term storage, leading to the alteration of SNF. 10 A 10-year long drip-test conducted in the 1990s has confirmed that SNF undergoes the same oxidation–hydration alteration pattern to that of uraninite.…”